Geosoft - Exploring With Data

Displaying Grid Profiles along a Section

When displaying grid profiles, sometimes you need to combine your data in one display that includes multiple scales. In this post, I’ll review an option that makes it easier to deal with this challenge.

Using Target or the Oasis montaj Drillhole extension, you can add profiles to section maps.

Depending on the scale of your section and the page size you are working with, it can be difficult to see subtle features in the gridded data. If this is the case, it is helpful to know that there is another way to see the profiles of gridded data along a section.

1. Plot the section trace on a plan map

2. Use Grid Profile to save various grid values along the trace to a new line in a new or existing database. I prefer a *new* database as there will be a new channel for each grid.

3. Display the profiles for each channel and customize the visualization of the profile to your preference. (To do this, right click on the profile and select Profile Options...)

4. Right click and select Plot Profile Figure... 

and this will display your grid profiles along the section in a new map.

What is Magnetization Vector Inversion?

An exploration geophysicist asked us a couple of days ago, "What is this Magnetization Vector Inversion,or MVI, that Geosoft has recently released and that is generating so much interest?" We replied that Geosoft has online information about MVI, but on later reflection realized that there is still a need for a quick overview of the physical principles driving MVI, which leads us to this blog post.

We should first appreciate that geophysical methods aim to determine physical properties of rocks within the earth, and with modelled rock properties we can make better exploration decisions. The magnetic method in particular is sensitive to the magnetization property of rocks. Some rocks are more "magnetic" than others, and it is this contrast that we are able to map and model in 3D with the magnetic methods.

The physical principle behind Magnetization Vector Inversion is that magnetic material in the Earth is affected by the presence of the Earth's geomagnetic field. Basically, the Earth's field causes a perturbation of the magnetic domains in magnetic materials, for example, in rocks containing traces of magnetite. We can picture these magnetic domains as small magnetic dipoles which, in the absence of the Earth's geomagnetic field, might be oriented more or less randomly as shown in the upper layer of Figure 1, or in a more ordered manner as shown in the lower layer. In the presence of the Earth's geomagnetic field, the magnetic domains will orient themselves in some more ordered arrangement like that shown in Figure 2. The actual ordering is controlled by a number of interacting magnetic effects, including for example, induction, remanence, anisotropy, and demagnetization, amongst others.

Figure 1: In the absence of any external magnetic field, the magnetic domains (represented by green cones) might be oriented more or less randomly. The ordering of the magnetic domains depends on conditions during the rock's formation and subsequent history

Figure 2: In the presence of the Earth's geomagnetic field (represented by the red cone) the magnetic domains shown in Figure 1 will align themselves in a more ordered fashion.

Now, in terms of Magnetization Vector Inversion in VOXI, we invert magnetic field data to recover both magnetization direction and amplitude resulting in Earth models exactly like that shown in Figure 2. That is, the output from MVI is a set of vectors giving the directions and amplitudes of any magnetic domains in the survey area.

Many geophysicists are familiar with Susceptibility Inversion so it is worthwhile comparing Susceptibility Inversion with Magnetization Vector Inversion. Susceptibility Inversion is based on the premise that, in the presence of the Earth's geomagnetic field, the magnetic domains in all rocks orient themselves in the parallel to the Earth's geomagnetic field. That is, the domains shown in Figure 1 are hypothesized to orient themselves like that shown in Figure 3. When the magnetic domains all tend to align themselves with the Earth's geomagnetic field we have a mathematically simple situation, albeit quite unrealistic in the Earth. In this special situation we can take the ratio of the amplitude of the magnetization and normalize it by the Earth's geomagnetic field to yield the "susceptibility". The net magnetization direction associated with the magnetic domains is, then by definition, the Earth's geomagnetic field direction.

Figure 3: In Susceptibility Inversion, the presence of the Earth's geomagnetic field (represented by the red cone), is assumed to cause the magnetic domains to align parallel to the external field.

Susceptibility is a useful quantity for describing the magnetic properties of a limited class of homogeneous isotropic materials, however, it is well known that the Earth is composed of complicated, heterogeneous material on a wide range of length scales. This makes it much more likely that the magnetic domains in Earth material will not be aligned with the Earth field direction and that susceptibility inversion might give a first approximation to the true Earth, but will fail in many Exploration situations. Nevertheless, because susceptibility is a well-studied and tabulated measure for homogeneous laboratory samples, in VOXI output we normalize the amplitude of the magnetization vectors by the Earth's geomagnetic field. With this normalization, the amplitude of the vectors will be equal to the corresponding susceptibility in the special case that the Earth was indeed homogeneous and isotropic, that is, if magnetic domains were aligned with the Earth's geomagnetic field.

In summary, based on the physical properties of rocks, Magnetization Vector Inversion is designed to recover both the amplitude and direction of magnetic domains and therefore provides an accurate and robust description of the magnetic properties of rock in the Earth. Experience to date demonstrates that Magnetization Vector Inversion supports effective and efficient Exploration.

Software upgrade available - August 21, 2012

The following Geosoft software upgrades are now available to all maintained customers:

• Oasis montaj 7.5.1
• Oasis montaj - Educational 7.5.1
• Target 7.5.1
• Target for ArcGIS 3.5.1
• Geochemistry for ArcGIS 2.5.1
• Plug-in for ArcGIS 2.5.1 (this is a free product, no maintenance is required)

This release includes support for ArcGIS 10.1 as well as a number of maintenance fixes.  Click the Geosoft Product above to see detailed release notes for this software upgrade and instructions on how to update.

GM-SYS 3D Modelling with Velocity Volumes

Geosoft demonstrated the latest features in our GM-SYS 3D gravity modelling software at this year’s EAGE in Copenhagen. Topping the list of what’s new is 3D hybrid density model support.

With the latest version, GM-SYS 3D Modelling v7.5, you can create 3D gravity models that incorporate a velocity volume from a 3D seismic survey. Previously you were limited models with horizons extracted from density cube and constant density layers like this one:

When integrating with seismic reflection surveys, models are defined as velocity or density cubes. The filled density voxel shown above was created from a velocity model in SEG-Y format. Seismic interpreters commonly provide velocity models to potential-field professionals as an exchange format. Velocity information must then be converted to density using known relationships between parameters. The Velocity to Density conversion utility was introduced in v7.2 and enables easy conversion between density and velocity allowing selection from ten of the most commonly-used, published relationships.

In GM-SYS 3D Modelling v7.5 we can build models using 3D density distributions, like this one with a 3D density distribution below the bathymetry (bathymetry is shown by the pink surface near the top of the model).

This new density distribution can be used for forward modelling of gravity and gravity gradiometry data with a more accurate representation of the density distribution in a 3D model.

Adding Bing Maps imagery to Geosoft maps

Bing Maps published its largest satellite release to date this past month, and with Geosoft’s latest software release, Oasis montaj and Target 7.5, Bing Maps imagery can be added as a map group.

Bing Maps is a web mapping service provided as a part of Microsoft's Bing suite of search engines and powered by the Bing Maps for Enterprise framework. Bing’s satellite release adds 165 terabytes of new data which cover 38 million square kilometres. Imagery from North America, South America, Africa, Australia, Europe and Asia are included.

To access the Bing Maps service within Geosoft, go to Seek Data > Add Bing Maps Imagery. You can add Aerial, Road or a Hybrid image as a map group. Note that you will need to be connected to the Internet and logged in with your Geosoft ID. Use of the service is subject to Microsoft's data license requirements. Learn more in this How-To article. 

When you are offline, a grey disconnected image will appear in place of the Bing Maps layer until you connect again. As the Bing Maps map group is powered by an online service, your map will display the latest data every time you use it.

Learning exchange at China’s Jilin University

Geosoft recently visited Jilin University in Changchun, the capital city of Jilin Province in Northeast China, to conduct a five-day software training session for professors and students in the university's geoscience program.

Founded in 1946, Jilin University is a leading national university in China. The university's College of Geo-exploration Science and Technology was established 10 years ago, but the Department of Geophysics that is affiliated with it has a history that dates back to the 1950's. Jilin's Applied Geophysics program has gained recognition for its progressive teaching of both theory and application. In 1988, Applied Geophysics was elected as one the State Key Disciplines, the only one of its kind in China.

Geosoft software, including Oasis montaj and GM-SYS gravity modelling, has been utilized within Jilin University geoscience teaching program for several years and professors were keen to have students become more proficient with the software's core geophysical mapping and analysis capabilities. For Jilin post-graduate students working on their thesis projects, it was an opportunity to learn how to apply some of Geosoft's advanced gravity and magnetic interpretation features to their work.

Held in Jilin's historical geophysics department facility, a former Emperors palace, the training session provided an opportunity for both educational and cultural exchange. "It was quite a contrast, training 55 students and professors to use modern day exploration technology in such an historic setting," said training leader Beti Slakeska, data manager, special projects with Geosoft Australia. She was assisted in the training program by Sophie He, with MaiQin, Geosoft's authorized business partner in China.

"The students were very excited to visualize their projects in the Oasis montaj platform," said Beti. "Some of the trainees had never used Oasis montaj before, and by the end they were all capable of gridding data and creating 3D maps. It was rewarding to see how pleased the students were with their results."

The learning went both ways. "There was lots of discussion in and out of the training session," said Beti. "In China, there is such respect for education, and joy in acquiring new knowledge. By the end of my stay, I'd also learned a new skill: how to fly a Chinese kite!"

When they complete their studies, the next generation of resource exploration students will be able to put Geosoft to work in China's all-important and growing resource sector.

Drag and drop shortcuts in Oasis montaj - time savers and hidden gems

A question came through our twitter feed asking what is the best way to import many XYZ files into Oasis montaj.  The answer:  Select all the XYZ files in Windows Explorer, drag them and drop them into a new, empty Geosoft database.  

There are several useful drag-and-drop shortcuts in Oasis montaj and Target, but because of their nature (they are drag-and-drop methods after all!), they can often be overlooked when they are most helpful. 

Drag-and-drop can be used to:

Simplify multi-file operations:

• Drag-and-drop a Geosoft map, grid, or database from Windows Explorer into Oasis montaj.  This is a quick way to add files to a new Project.
• Drag-and-drop a map, grid, or database from the Project Explorer to the Oasis montaj desktop. This is a quick way to open these file types.
• Drag-and-drop XYZ files to a new database.

Move map groups from one map to another:

• Drag-and-drop a grid from the Project Explorer to an open map.  (This is the same as Display Single grid, and if the auto-shading option is on, the dropped grid will be shaded.)
• Drag-and-drop a single map group from one map to another map. (This is the same as right-click option to Copy and Paste Georeferenced.)

Transfer map layers from 2D maps to 3D views:

• In Oasis montaj 7.5 you can drag and drop map layers from Target section maps to the 3D Viewer and the layers will appear georeferenced in 3D space. 

You can see some of these drag-and-drop methods in action in this video.

3D Earth Modelling in the Cloud: The Geosoft VOXI development story

Released in April, 2012, Geosoft’s VOXI Earth Modelling service gives exploration geophysicists the ability to convert magnetic and gravity data directly into useful 3D Earth models that can be integrated with other 3D exploration data.

Creating the cloud-based VOXI inversion service took us over three years, and required the work of 29 people on a number of development teams. This is the story of how we did it.

3D Earth Modelling and Exploration

Three-dimensional Earth modelling of geophysical data has been an important part of exploration geophysics for over a decade, allowing explorers to transform 2D data into detailed, subsurface 3D models useful for defining exploration targets in areas of complex geology.

The science behind 3D inversions has been in development within academic environments even longer. The University of British Columbia Geophysical Inversion Facility (UBC-GIF), a leader in this area of research, was founded in 1989. The UBC-GIF consortium for Joint and Cooperative Inversion of Geophysical and Geological Data (JACI) pioneered the developed practical inversion algorithms that have been used in real exploration since the 1990s.

It’s our view, however, that the full potential for 3D inversion in exploration has continued to be limited both by the complexity of the tools and the need for powerful computers. With VOXI, our goal was to address both of these challenges and make 3D Earth Modelling accessible to more explorers and be more impactful to exploration success.

Behind VOXI’s development

VOXI development began in 2009, the year Dr. Robert G. Ellis joined Geosoft as a Senior Scientist for Earth Modelling. As a co-founder of the UBC-GIF, and a collaborator with UBC and other modelling groups over 20 years, Rob is a renowned expert in 3D geophysical inversion. Rob and Geosoft embarked on a shared mission: to build the next generation 3D earth modelling system that would combine Rob’s accumulated knowledge with the latest available algorithms and commercial development techniques in use at Geosoft.

We also saw the opportunity to harness cloud computing to provide super-computing power to everyone. The cloud presented us with both challenge and opportunity. Using cloud computing meant interpreters would not be limited by the processing power of their computers, which is a huge benefit for process-intensive applications like 3D inversion. Our challenge was to scale VOXI so that hundreds of geophysicists could run large inversions at the same time, and from anywhere in the world.

Scaling for cluster computing

With Rob's knowledge of the science of 3D inversion, in less than 6 months we were able to build the latest generation of inversion from both open-source libraries and our own original development. Then came what turned out to be the really hard work – making the system work on multiple-cores in a cloud environment, and making it easy to use.

Our first scaling work was done on a conventional 96-core computing platform hosted in the “cloud” by Rackspace in the USA. All our multi-threading and cluster-computing development was proven here, and we were able to achieve some impressive performance numbers with Ivanhoe Mines as a key early collaborator accessing the service from Australia.  But we still faced the challenge of how to make VOXI scale so that many geophysicists could run large inversions at the same time, and from anywhere in the world. For that we turned to the Microsoft Azure platform.

True Cloud computing

Azure was important to us in a number of ways. First and foremost was the level of commitment that Microsoft has made to Azure, which has the ability to support our exploration customers anywhere on earth with 6 international data centers, each with up to 3 million processing cores. Microsoft also had both the business models and the tools we needed to be able to scale as demand required.

But developing for a true cloud platform is not straight-forward, as we would find out.  Building a multi-core cloud-based algorithm is very different from building a program that runs on a workstation or local cluster. The effort to re-engineer VOXI for Azure took us most of a year to get right.

Making VOXI usable

And as any commercial software company knows, building software to be usable is a challenge in its own right. We worked very hard with our collaborators over two years to design and improve the interface so that everything would work as smoothly as possible and fit within an explorer's natural workflow. The user-interface development work required yet another full-time development team.

Summary of the benefits

We feel the outcome has been well-worth the journey, and we are excited about the benefits we see for exploration:

• All explorers have super-computer access to build large models in minutes.
  One early VOXI customer compared the VOXI service performance to his current desktop modelling program. Given exactly the same model, what took four hours with his current software was completed by VOXI in under 2 minutes - more than 100 times faster.
   
• 3D Earth modelling is now practical and user-friendly for all geophysicists.
  VOXI runs with a minimum of user effort directly from Geosoft Oasis montaj, an industry-standard platform for working with geophysical data.  It just works, naturally, and seamlessly.

What’s Next?

VOXI has been our largest and most comprehensive development to date. The work we have done with VOXI lays the foundation we need to build more useful cloud capabilities for explorers in the years to come, including more 3D modelling methods, support for larger models and new ways to harness cloud computing to benefit exploration.

Free Sources of Geoscience Data

Occasionally I am asked about my favourite (and most useful) sources of publicly available online data. Here are some of the ones I’ve used and can recommend:

• If you are working in Canada, the Geological Survey of Canada’s Geoscience Data Repository is a great source for regional and survey scale datasets.  It includes extensive Aeromagnetic and Electromagnetic data with simple instructions for viewing and downloading the data using a mapping application that is based on Geosoft DAP technology.


• Many global scientific and government organization host data online, or you can order it (sometimes for a small processing fee). A few that I have used include: Geoscience Australia - this site has many geophysical and geological datasets; USGS EROS Center - links to several data discovery tools; NOAA National Geophysical Data Center - Data by Discipline links to some great resources; and USGS LP DAAC - links to resources for ASTER data.


• Provincial and state geoscience surveys are also a great source of geoscientific data.  I recently attained a copy of New South Wales’ Explorers Directory 2012 with GIS data in Esri and MapInfo formats and a great selection of imagery.  For cultural and geographic data, the datasets provided with Esri and MapInfo applications are a good start. In the US, data.gov has a growing collection of spatial data in many formats.


• Compilations are often sponsored by a group of government and educational groups to make data publicly available and easily accessible, including numerous programs like Geomagnetism, a NOAA/CIRES project;  OneGeology, an international effort to collect geological data at 1:1 million scale; and ASTER GDEM, a joint NASA JPL program to collect high resolution ASTER data for the world.

I’ve posted on the Geosoft DAP Server before.  The SRTM data on the Geosoft DAP Server is very handy, and there are some other large, low-res datasets available here as well. Datasets can be windowed and reprojected and reformatted as needed with very little effort. 

I hope you find this list helpful. I’d be interested in hearing about some of your favourites!

Target for ArcGIS Sneak Peek

The Geosoft 2012 release will be available soon. One of the improvements that I am most excited about are three interconnected features in Target for ArcGIS that connect Sections to 3D.

Display: You can send map layer(s) from a Target for ArcGIS data frame to the Geosoft 3D Viewer. Layers from Sections or Plans will appear in their correct geospatial orientation in the 3D view.

Export: You can export 2D interpretations from Section or Plan to 3D Shapefiles or 3D DXF files. These new 3D files can be opened in the Geosoft 3D Viewer, Esri ArcScene, and other 3D applications.

Import:  You can include 3D Shapefiles and 3D DXF files when generating a Target for ArcGIS Section. These 3D files will appear correctly located on the Section.  3D DXF files are sliced to display the intersection with the Section; the entire 3D Shapefile is projected on to the centre slice of the Section.

These new capabilities improve the connection between 2D and 3D in Target for ArcGIS.